The local farmers I buy from are very honest about the quality. They will tell you if it's suitable for horse, rabbits or better for cattle, mulch, etc. Someone recently placed an ad in our local papaer 'poor quality hay for sale cheap - suitable for cows and mulch'. I thought it was pretty funny.
You may need to see the hay, ask how it;s stored, check if there are big coarse bits in it. Once I get it home, I usually pull off a flake or 2 at a time and check it for weeds, stalks and pull those out. I have one who will eat local hay and the others want Oxbow.